How Does Temperature Affect Humidity?
One thing you need to know about humidity, especially when you are thinking about the humidity levels in your home, is temperature. Temperature has a direct effect on the humidity levels whether it’s inside or outside your home.
If you are trying to control the humidity of your home, either through humidifiers or dehumidifiers, but have not been able to get the percentages right, then you may not have taken the temperature into account.
You may also not know what equilibrium and relative humidity mean. Both of these terms are important when you are measuring the humidity and will help you to better understand the humidity levels.
Before we can understand the relationship between air temperature and relative humidity, or even what relative humidity is, we need to understand what equilibrium is.
We know that water vapor condenses to form a liquid and that it evaporates to form a gas (at least, we should all know this).
When condensation occurs, it occurs more quickly when there is more water vapor. The same is true for evaporation; the more water there is, the faster it will evaporate.
Somewhere in the middle of these two processes, there comes the point where water is evaporating as fast as it is condensing. This is the equilibrium point.
When the equilibrium point is reached, the air is said to be ‘saturated’ with water vapor. If you change nothing, then the equilibrium point is held. However, if you change the temperature, the equilibrium point will also change.
If you increase the temperature, then evaporation is quickened. The hotter it is, the more water can evaporate, and the balance is shifted more in water vapor’s favor. This means that when the air is hotter, the air can hold more water vapor.
When the air is hotter, the equilibrium point will be able to hold more water vapor than it did at the lower temperature. A higher temperature of air must hold more water vapor before it is saturated.
Relative Humidity and Temperature
Relative humidity is important for measuring humidity as the amount of water vapor in the air will change depending on the temperature.
When we talk about the relative humidity, we are comparing the water vapor percentage of the air against what it could hold if it were saturated.
Remember when the air is saturated, it is holding as much water vapor as is possible.
So, when we say that the relative humidity is 45 percent, we are saying that the air is holding 45 percent of the possible water vapor if the air was saturated. As you increase the temperature, the amount of water vapor which can be held is increased and the relative humidity will decrease.
What Does This Mean For Me?
When you walk through a room and feel the wetness or dryness of the air, you are feeling the relative humidity. Your comfort level is determined by this relative humidity.
Anything below 25 percent will feel dry to your skin, nose, and throat. Anything above 60 percent will feel wet. Above 70 percent and you start to lay the foundation for mold and rot.
Remember, the amount of water vapor in the air may change, but the relative humidity can stay the same. We are not worried about how much water vapor is in the air, but, instead, we are concerned about how much water vapor is in the air in relation to the temperature of the air.
I have already talked about what happens to the relative humidity when the temperature goes up, but what about when it goes down?
If you decrease the temperature, then the relative humidity will increase.
If the temperature goes down enough without the water vapor amount changing, then you will eventually reach 100 percent relative humidity. At this point, water will start to condense and form dew.
The temperature at which the dew begins to form is known as the dew point. This is what causes due to form on grass in the early morning or condensation on your windows.
In Your Home
Every homeowner should measure their relative humidity (especially if you can feel that the air is particularly wet or dry).
Too much moisture can cause paint and wallpaper to fall from the walls. The moisture can also increase the growth of bacteria and mold in wood and drywall. This, in turn, can attract pests into your home.
Too much moisture can also bend and swell wood, leasing to uneven floors and walls. The air can also feel sticky and muggy.
If the relative humidity goes the other way and the air becomes too dry, you or your family can suffer from more colds, nosebleeds, and dry skin. The air can also have a dry feel to it which can be comfortable.
Try to maintain a relative humidity of around 45 percent in your home for a comfortable environment.
Now that I have got the science stuff out of the way, you can see why it is critical for you to measure the relative humidity in your home. It is all very well to add more moisture to your home or remove moisture from the air, but if you are not doing this in relation to the temperature of your home, you are not going to be hitting the numbers which will bring you the most comfort.
Investing in a hygrometer can help you to keep the balance in your home. You should always remember that the humidity in your home is going to be different in the summer as it is going to be in the winter and plan accordingly.
A little science can be daunting, but by understanding how the vapor levels in the air actually work, you can better plan how you are going to create a safe environment for your family.